Polygonal fuel cell apparatus and method of making

ABSTRACT

In one embodiment of the present invention, a polygonal fuel cell comprises: a cathode layer having a tubular shape; a contact layer electrically coupled to and disposed on the cathode layer to leave an uncovered cathode surface portion; an electrolyte layer disposed on the uncovered cathode surface portion; and an anode layer electrically isolated from the contact layer, disposed on the electrolyte layer such that the polygonal fuel cell has a polygonal cross section to facilitate dense packing.

BACKGROUND OF INVENTION

The present invention relates generally to the field of fuel cells andmore specifically to fuel cells with polygonal cross-sections.

In a wide variety of applications, fuel cells are used to providerelatively cleaner and higher efficiency electrical power compared tofossil fuel burning electrical power plants.

Two design geometries have come to dominate the fuel cell field: theflat plate design and the circular tubular design (see, for example,Fuel Cell Handbook (Fifth Edition), Chapter 8, EG&G Services, availablefrom National Technical Information Service, U.S. Department ofCommerce, Springfield, Va.). The flat plate design has an advantage ofhigh power density but suffers a disadvantage of being difficult to sealagainst gas leakage. Conversely, the circular tubular design offers thebenefit of a more reliable gas seal, but at the cost of a reduced powerdensity. An opportunity exists, therefore, to design a new fuel cellgeometry which will retain the gas sealing performance of the circulartubular design while approaching the power density of the flat platedesign.

SUMMARY OF INVENTION

The opportunity described above is addressed, in one embodiment of thepresent invention, by a polygonal fuel cell comprising: a cathode layerhaving a tubular shape; a contact layer electrically coupled to anddisposed on the cathode layer to leave an uncovered cathode surfaceportion; an electrolyte layer disposed on the uncovered cathode surfaceportion; and an anode layer electrically isolated from the contact layerand disposed on the electrolyte layer such that the polygonal fuel cellhas a polygonal cross section.

BRIEF DESCRIPTION OF DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 illustrates an isometric projection of a polygonal fuel cell inaccordance with one embodiment of the present invention;

FIG. 2 illustrates an end view orthographic projection of the polygonalfuel cell in accordance with a more detailed embodiment of theembodiment illustrated in FIG. 1;

FIG. 3 illustrates an end view orthographic projection of the polygonalfuel cell in accordance with another more detailed embodiment of theembodiment illustrated in FIG. 1;

FIG. 4 illustrates an end view orthographic projection of the polygonalfuel cell in accordance with still another more detailed embodiment ofthe embodiment illustrated in FIG. 1;

FIG. 5 illustrates an end view orthographic projection of a polygonalfuel cell stack in accordance with another embodiment of the presentinvention;

FIG. 6 illustrates an end view orthographic projection of a polygonalfuel cell stack in accordance with a more detailed embodiment of theembodiment illustrated in FIG. 5; and,

FIG. 7 illustrates an end view orthographic projection of a polygonalfuel cell stack in accordance with another more detailed embodiment ofthe embodiment illustrated in FIG. 5.

DETAILED DESCRIPTION

In accordance with one embodiment of the present invention, FIG. 1illustrates an isometric projection of a polygonal fuel cell 100comprising a cathode layer 110, a contact layer 120, and an anode layer140. Cathode layer 110 has a tubular shape through which an oxidant gasflows in operation. Contact layer 120 is electrically coupled to cathodelayer 110 to provide an external electrical contact and is disposed toleave an uncovered cathode surface portion. Electrolyte layer 130,disposed on the uncovered cathode surface portion, and anode layer 140,electrically isolated from contact layer 120 and disposed on electrolytelayer 130, complete polygonal fuel cell 100. In operation, fuel gasflows over anode layer 140.

Anode layer 140 is disposed on electrolyte layer 130 such that polygonalfuel cell 100 has a polygonal cross section. Compared to a circulartubular design, the tubular shape of cathode layer 110 providescomparable gas sealing capability, while the polygonal cross sectionpermits denser packing into fuel cell stacks.

As used herein, “polygonal” refers to the shape of a plane geometricpolygon, optionally with rounded corners. While sharp-cornered polygonsprovide the highest power density, practical considerations ofmanufacturability and strength may favor rounded corners for someapplications.

In accordance with a more detailed embodiment of the embodimentillustrated in FIG. 1, FIG. 2 illustrates an end view orthographicprojection of polygonal fuel cell 100 wherein the polygonal crosssection is an equilateral hexagon. FIG. 2 also illustrates a still moredetailed embodiment of the embodiment illustrated in FIG. 1, in whichpolygonal fuel cell 100 comprises two contact layers 120 disposed onadjacent polygonal faces to facilitate stacking.

In accordance with another more detailed embodiment of the embodimentillustrated in FIG. 1, FIG. 3 illustrates an end view orthographicprojection of polygonal fuel cell 100 wherein the polygonal crosssection is a square (i.e., an equilateral rectangle).

In accordance with still another more detailed embodiment of theembodiment illustrated in FIG. 1, FIG. 4 illustrates an end vieworthographic projection of polygonal fuel cell 100 wherein the polygonalcross section is an equilateral triangle.

In accordance with another embodiment of the present invention, FIG. 5illustrates an end view orthographic projection of a portion of apolygonal fuel cell stack 200 comprising: a plurality of polygonal fuelcells 100, a cathode bus 170, an anode bus 180, and a plurality ofinterconnection strips 160. As described above, polygonal fuel cells 100comprise contact layers 110 and anode layers 140 and have a polygonalcross section to facilitate dense packing. Each polygonal fuel cell 100produces a characteristic voltage rise and is capable of sourcingcurrent only up to a safe individual cell current limit. In order tomeat overall requirements of polygonal fuel cell stack 200. therefore,polygonal fuel cells 100 are electrically coupled in parallel to satisfya current requirement and in series to satisfy a voltage requirement.Stack voltage is made available externally by electrically couplingcathode layers 110 to cathode bus 170 and by electrically coupling anodelayers 140 to anode bus 180. cell-to-cell and cell-to-bus electricalcoupling as achieved by interposing interconnection strips 160 therebetween. interconnection strips 160 also provide spacing among polygonalfuel cells 100 to permit gas flow over anode layers 140.

In a more specific embodiment, FIG. 5 also shows polygonal fuel cellstack 200 wherein the polygonal cross section is an equilateral hexagonand wherein each of polygonal fuel cells 100 comprises two of contactlayers 120 disposed on adjacent polygonal faces.

In accordance with a more detailed embodiment of the embodimentillustrated in FIG. 5, FIG. 6 illustrates an end view orthographicprojection of a polygonal fuel cell stack wherein the polygonal crosssection is a square (i.e., an equilateral rectangle).

In accordance with another more detailed embodiment of the embodimentillustrated in FIG. 5, FIG. 7 illustrates an end view orthographicprojection of a polygonal fuel cell stack wherein the polygonal crosssection is an equilateral triangle.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A polygonal fuel cell comprising: a cathode layer having a tubularshape; a contact layer electrically coupled to and disposed on saidcathode layer to leave an uncovered cathode surface portion; anelectrolyte layer disposed on said uncovered cathode surface portion:and an anode layer electrically isolated from said contact layer,disposed on said electrolyte layer such that said polygonal fuel cellhas a polygonal cross section.
 2. The polygonal fuel cell of claim 1wherein said polygonal cross section is selected from the groupconsisting of triangles, rectangles, and hexagons.
 3. The polygonal fuelcell of claim 1 wherein said polygonal cross section is equilateral. 4.The polygonal fuel cell of claim 1 comprising two of said contact layersdisposed on adjacent polygonal faces, wherein said polygonal crosssection is a hexagon.
 5. A polygonal fuel cell comprising: a cathodelayer having a tubular shape; a contact layer electrically coupled toand disposed on said cathode layer to leave an uncovered cathode surfaceportion; an electrolyte layer disposed on said uncovered cathode surfaceportion; and an anode layer electrically isolated from said contactlayer, disposed on said electrolyte layer such that said polygonal fuelcell has a polygonal cross section selected from the group consisting ofequilateral triangles, squares, and hexagons.
 6. The polygonal fuel cellof claim 5 comprising two of said contact layers disposed on adjacentpolygonal faces, wherein said polygonal cross section is a hexagon.
 7. Apolygonal fuel cell stack comprising: a plurality of polygonal fuelcells comprising contact layers and anode layers, having a polygonalcross section, and being adapted to be electrically coupled in parallelto satisfy a current requirement and in series to satisfy a voltagerequirement; a cathode bus adapted to electrically couple said contactlayers; an anode bus adapted to electrically couple said anode layers;and a plurality of interconnection strips adapted to electrically couplesaid polygonal fuel cells, said cathode bus, and said anode bus.
 8. Thepolygonal fuel cell stack of claim 7 wherein said polygonal crosssection as selected from the group consisting of triangles, rectangles,and hexagons.
 9. The polygonal fuel cell stack of claim 7 wherein saidpolygonal cross section is equilateral.
 10. The polygonal fuel cellstack of claim 7 wherein each of said polygonal fuel cells comprises twoof said contact layers disposed on adjacent polygonal faces, whereinsaid polygonal cross section is a hexagon.
 11. A polygonal fuel cellstack comprising: a plurality of polygonal fuel cells comprising contactlayers and anode layers, having a polygonal cross section, and beingadapted to be electrically coupled in parallel to satisfy a currentrequirement and in series to satisfy a voltage requirement; a cathodebus adapted to electrically couple said contact layers; an anode busadapted to electrically couple said anode layers; and a plurality ofinterconnection strips adapted to electrically couple said polygonalfuel cells, said cathode bus, and said anode bus. said polygonal crosssection being selected from the group consisting of equilateraltriangles, squares, and equilateral hexagons.
 12. The polygonal fuelcell stack of claim 11 wherein: each of said polygonal fuel cellscomprises two of said contact layers disposed on adjacent polygonalfaces; and said polygonal cross section is a hexagon.
 13. A method ofmaking a polygonal fuel cell comprising: providing a cathode layerhaving a tubular shape; electrically coupling arid disposing a contactlayer on said cathode layer to leave an uncovered cathode surfaceportion; disposing an electrolyte layer on said uncovered cathodesurface portion; and disposing an anode layer, electrically isolatedfrom said contact layer, on said electrolyte layer such that saidpolygonal fuel cell has a polygonal cross section.
 14. The method ofclaim 13 wherein said polygonal cross section is selected from the groupconsisting of triangles, rectangles, and hexagons.
 15. The method ofclaim 13 wherein said polygonal cross section is equilateral.
 16. Themethod of claim 13 wherein electrically coupling and disposing a contactlayer on said cathode layer comprises electrically coupling anddisposing two of said contact layers on adjacent polygonal faces,wherein said polygonal cross section is a hexagon.
 17. A method ofmaking a polygonal fuel cell comprising: providing a cathode layerhaving a tubular shape; electrically coupling and disposing a contactlayer on said cathode layer to leave an uncovered cathode surfaceportion; disposing an electrolyte layer on said uncovered cathodesurface portion; and disposing an anode layer, electrically isolatedfrom said contact layer, on said electrolyte layer such that saidpolygonal fuel cell has a polygonal cross section selected from thegroup consisting of equilateral triangles, squares, and equilateralhexagons.
 18. The method of claim 17 wherein: electrically coupling anddisposing a contact layer on said cathode layer comprises electricallycoupling and disposing two of said contact layers on adjacent polygonalfaces; and said polygonal cross section is a hexagon.
 19. A method ofmaking a polygonal fuel cell stack comprising: electrically coupling aplurality of polygonal fuel cells, in parallel to satisfy a currentrequirement, in series to satisfy a voltage requirement, by interposinga plurality of interconnection strips therebetween, said polygonal fuelcells comprising contact layers and anode layers and having a polygonalcross section; electrically coupling a cathode bus to said contactlayers by interposing a plurality of interconnection stripstherebetween; and electrically coupling an anode bus to said anodelayers by interposing a plurality of interconnection stripstherebetween.
 20. The method of claim 19 wherein said polygonal crosssection is selected from the group consisting of triangles, rectangles,and hexagons.
 21. The method of claim 19 wherein said polygonal crosssection is equilateral.
 22. The method of claim 19 wherein: each of saidpolygonal fuel cells comprises two of said contact layers disposed onadjacent polygonal faces; and said polygonal cross section is a hexagon.23. A method of making a polygonal fuel cell stack comprising:electrically coupling a plurality of polygonal fuel cells, in parallelto satisfy a current requirement, in series to satisfy a voltagerequirement, by interposing a plurality of interconnection stripstherebetween, said polygonal fuel cells comprising contact layers andanode layers and having a polygonal cross section; electrically couplinga cathode bus to said contact layers by interposing a plurality ofinterconnection strips therebetween; and electrically coupling an anodebus to said anode layers by interposing a plurality of interconnectionstrips therebetween. said polygonal cress section being selected fromthe group consisting of equilateral triangles, squares, and equilateralhexagons.
 24. The method of claim 23 wherein: each of said polygonalfuel cells comprises two of said contact layers disposed on adjacentpolygonal faces; and said polygonal cross section is a hexagon.